Does anybody use the bottom intake fan found in many cases? the one right next to the bottom-mounted PSU.

for those of you who have, do you find routing cables around the fan to be an issue? also, do you find the usefulness of the fan to be reduced because of the GPU partially/completely blocking it off from the CPU part of the case? how about when using open-air GPU coolers?

I honestly wouldn't use it unless you have a good filter over it. This is where the majority of dust going into your system is going to come from. I wouldn't worry so much about cables being in the way or disrupting air flow though, nor the gpu. It would probably help move more of that hot air to the top of the case to be exhausted, which is probably what the best use of a bottom fan would be. If you want good air flow for the bottom of your case without sucking in dust I suggest getting one of these antec spot cool fans for $11. You can stick it anywhere you want. Its also fairly quiet for the amount of air it can move. 3 speed switch on the fan itself and it also works great with a fan controller.Buy ANTEC [SPOT COOL] Antec Spot Cool Adjustable System Cooler Blue LED 3 Speed 2000-3000RPM 23-33DBA 15-22CFM

My case has a dual rad setup at the top and bottom of the case. I originally had the airflow bottom to top, bottom fans blowing up and the top rads blowing out the top. I found though some of the stuff on the mobo was getting quite warm so I changed the airflow direction since the top rad fans are right next to the mobo they washed over the mobo better. Having the bottom being an intake noticeably did increase the dust accumulation in the case but it wasn't drastic. If it works out well with your airflow scheme and you're willing to take it out to the garage to blow it out a little more often then I wouldn't consider it a deal breaker.